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This report describes the prevalence and trends of neural tube defects (NTD) in Australia during the past decade. The best estimated prevalence of NTD among pregnancies is presented based on the information from states that collect near complete data on NTD. Characteristics and outcomes of the births and pregnancy characteristics of mothers are presented for the period 199-2008. The purpose of compiling this national report is to provide baseline prevalence of NTD, before implementation of mandatory folic acid fortification of bread flour in September 2009.

Summary

Background

Neural tube defects (NTDs) are a group of major congenital anomalies comprising anencephaly, spina bifida and encephalocele that result from very early disruption in the development of the brain and spinal cord. These conditions are often incompatible with life. Survivors frequently require intensive, costly, lifelong health and social care.

There is strong evidence of substantial reductions in the prevalence of NTD-affected pregnancies among women given periconceptional folic acid. Information about the benefits and programs promoting dietary and/or supplemental folic acid intake by women before and during pregnancy have existed in Australia for over 20 years. Voluntary fortification of foods with folic acid has been permitted in Australia since 1995. These measures have resulted in a very modest increase in folic acid consumption overall by women of childbearing age.

In Australia, from 13 September 2009, the mandatory folic acid fortification standard requires the addition of folic acid to all wheat flour for bread making, with the exception of organic bread, within the prescribed range of 200–300 μg per 100 g of flour. The main benefit is the primary prevention of NTDs.

This report updates the baseline prevalence of NTDs in Australia using data for the years from 2006 to 2008. These precede the implementation of mandatory folic acid fortification of bread flour. It is expected that the information provided in this report will help evaluate the impact of mandatory folic acid fortification on the prevalence of NTDs in the future.

Key findings

The results demonstrate four key aspects of the overall prevalence of NTDs that have implications for monitoring the effects of bread flour fortification.

A continued downward trend was observed in the overall prevalence of all NTDs. Between 1998 and 2008 the average annual decline in the overall prevalence of NTDs was 0.22 NTD per 10,000 births per year.

There were different trends in the overall prevalence of individual NTDs, i.e. anencephaly, spina bifida and encephalocele. Between 1998 and 2008 there was a fall in the overall prevalence of spina bifida, but no appreciable change in the overall prevalence of anencephaly or encephalocele.

There was unequal distribution of the NTD overall prevalence across the population with higher prevalence of NTD-affected pregnancies at extremes of reproductive age, that is, among women in the youngest and oldest age groups; among women living in areas of relative disadvantage; among women living in remote areas; and among women of Aboriginal and Torres Strait Islander origin.

Reduced overall prevalence of NTDs does not necessarily reduce birth prevalence of NTDs. Rising birth prevalence of NTDs was seen between 2005 and 2008 in the context of lower overall prevalence of NTDs in Victoria and there was no evidence of change in the overall prevalence of NTDs in New South Wales.